Poster 103: Proximal Shoulder Muscle Recruitment with Blood Flow Restriction Exercise Under Various Occlusion Conditions: Is More Pressure Really Better?

Objectives: Blood Flow Restriction (BFR) training provides partial occlusion at the proximal upper and lower extremities has been shown to improve muscular strength hypertrophy following an injury or surgery. By eliciting hypoxic intramuscular conditions, we can stimulate adaptive processes in skeletal muscle a similar manner high intensity resistance but substantially safer exercise workloads (20-30%1RM). While much of literature focused on tissues distal site occlusion, recent findings (Lambert et al 2021, Bowman 2020) have observed benefits (increased mass, work capacity, performance) extremity BFR shoulder region during rotator cuff both general population adults pitching athletes. These were partially attributed increased activation (via electromyography, EMG) while under occlusion. However, only one standardized pressure (50%LOP) was utilized these investigations as typical current literature. The purpose present study compare (EMG amplitude, EMGa) variable pressures order optimize application muscle-specific targeting for rehabilitation preventative training. Methods: Institutional review board approval first obtained. Fifteen healthy subjects (7 males 8 females; age 29.4 ± 4.26 y.o.) from sports medicine physical therapy clinic recruited consented participate this study. Individuals excluded if they had any pre-existing pathology dominant limb, active participation structured body weight regimen, history vascular compromise that may render use inappropriate. Each participant underwent 4 different experimental sessions, which included performing 3 common exercises failure limb; dumbbell scaption, cable external rotation (ER) @ 0°, internal (IR) 0°. Exercises completed with using automated tourniquet system (Delfi Medical Innovations®) pre-assigned (0, 25, 50, 75% LOP) each session. Load determined 20% one-repetition maximum (1RM) utilizing maximal voluntary isometric contraction (MVIC) test. EMGa data surface electrodes (Delsys, Natick, MA, US) recorded target muscles occlusive testing - anterior deltoid, middle posterior infraspinatus, teres minor, trapezius muscles. Repetitions (RTF) assessments discomfort (VAS, 0-10) various also collected analysis. Raw measures averaged across 30 contractions IR scaption well 20 ER normalization 5 calibration 0% LOP. A mixed model ANOVA repeated performed followed by Bonferroni post hoc test pairwise comparisons. Type I error set ∝=0.05. Results: EMG are presented Figure 1 demonstrating significant effect level all (p<0.05). Of note, continued increases not above 50%LOP exception minor (Figure 1A) deltoid 1C). As 2, decreases repetitions relative 0%LOP 75%LOP Also Table 1, linear increase increasing LOP (p<0.01). Conclusions: There appears be several distinct differences about complex based pressure; including trend heightened activity being concurrent indicate added leads greater utilization, enhancing selection prescription dependent targeted group. data, there element diminishing returns past 50% musculature studied, ultimately limiting efficacy stimulus when considering total achievable volume. limited study, paired those found athletic populations used establish guidelines suitable prevention.